THE MOLECULAR BASIS OF INHERITANCE
DNA REPLICATION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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catalyzes the unwinding of DNA double helix at replication fork
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binds to and stabilizes single stranded DNA until it is used as a template
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relieves overwinding strain ahead of replication fork
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removes RNA nucleotides of primer and replaces them with DNA nucleotides
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Detailed explanation-1: -Topoisomerase prevents the over-winding of the DNA double helix ahead of the replication fork as the DNA is opening up; it does so by causing temporary nicks in the DNA helix and then resealing it. As synthesis proceeds, the RNA primers are replaced by DNA.
Detailed explanation-2: -Topoisomerase: relieves overwinding strain ahead of replication forks by breaking, swiveling, rejoining DNA strands.
Detailed explanation-3: -Topoisomerases play critical roles in DNA replication, transcription, and chromosome structure by altering the topological state of DNA, . These enzymes are capable of relaxing supercoiled DNA and of decatenating interlocked DNA (Fig. 3.3. 1).
Detailed explanation-4: -The untwisting of the double helix by helicase causes additional twisting of the DNA molecule ahead of the replication fork. Topoisomerase is the enzyme that helps to relieve this strain by breaking, untwisting and rejoining the DNA strands.
Detailed explanation-5: -Topoisomerase I is proposed to work ahead of the replication fork to remove positive DNA supercoils, whereas topoisomerase II is proposed to work primarily behind the fork to remove precatenanes. In contrast to replication models, drug models place topoisomerase II ahead of DNA tracking systems.